| 1. |
- Ahlsson, Anders, et al.
(författare)
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Atrial function after epicardial microwave ablation in patients with atrial fibrillation
- 2008
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Ingår i: Scandinavian Cardiovascular Journal. - : Taylor & Francis. - 1401-7431 .- 1651-2006. ; 42:3, s. 192-201
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To study epicardial microwave ablation of concomitant atrial fibrillation and its effects on heart rhythm and atrial function during follow-up. DESIGN: The study included 20 open-heart surgery patients with concomitant atrial fibrillation. Transthoracic echocardiography with flow and tissue Doppler recordings was performed preoperatively and at 6 months postoperatively. Blood samples were obtained preoperatively and postoperatively for analysis of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and amino terminal precursor of brain natriuretic peptide (NT-proBNP). RESULTS: Fourteen of 19 patients (74%) were in sinus rhythm with no antiarrhythmic drugs at 12 months. All patients in sinus rhythm had preserved left and right atrial-filling waves through atrioventricular valves during atrial contraction. Tissue velocity echocardiography on patients in sinus rhythm showed preserved atrial wall velocities, atrial strain, and atrial strain rate. Levels of natriuretic peptides tended to decrease in patients with stable sinus rhythm at one year compared to patients in atrial fibrillation. CONCLUSIONS: Epicardial microwave ablation results in sinus rhythm in a majority of patients and seems to preserve atrial mechanical function
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| 2. |
- Ahlström, Christer, 1977-, et al.
(författare)
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Assessment of Suspected Aortic Stenosis by Auto Mutual Information Analysis of Murmurs
- 2007
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Ingår i: Engineering in Medicine and Biology Society, 2007. EMBS 2007. - 9781424407873 ; , s. 1945-1948
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Konferensbidrag (refereegranskat)abstract
- Mild sclerotic thickening of the aortic valve affects 25% of the population, and the condition causes aortic valve stenosis (AS) in 2% of adults above 65 years. Echocardiography is today the clinical standard for assessing AS. However, a cost effective and uncomplicated technique that can be used for decision support in the primary health care would be of great value. In this study, recorded phonocardiographic signals were analyzed using the first local minimum of the auto mutual information (AMI) function. The AMI method measures the complexity in the sound signal, which is related to the amount of turbulence in the blood flow and thus to the severity of the stenosis. Two previously developed phonocardiographic methods for assessing AS severity were used for comparison, the murmur energy ratio and the sound spectral averaging technique. Twenty-nine patients with suspected AS were examined with Doppler echocardiography. The aortic jet velocity was used as a reference of AS severity, and it was found to correlate with the AMI method, the murmur energy ratio and the sound spectral averaging technique with the correlation coefficient R = 0.82, R = 0.73 and R = 0.76, respectively.
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| 3. |
- Ahlström, Christer, et al.
(författare)
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Feature Extraction for Systolic Heart Murmur Classification
- 2006
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Ingår i: Annals of Biomedical Engineering. - : Springer Science and Business Media LLC. - 0090-6964 .- 1573-9686. ; 34:11, s. 1666-1677
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Tidskriftsartikel (refereegranskat)abstract
- Heart murmurs are often the first signs of pathological changes of the heart valves, and they are usually found during auscultation in the primary health care. Distinguishing a pathological murmur from a physiological murmur is however difficult, why an “intelligent stethoscope” with decision support abilities would be of great value. Phonocardiographic signals were acquired from 36 patients with aortic valve stenosis, mitral insufficiency or physiological murmurs, and the data were analyzed with the aim to find a suitable feature subset for automatic classification of heart murmurs. Techniques such as Shannon energy, wavelets, fractal dimensions and recurrence quantification analysis were used to extract 207 features. 157 of these features have not previously been used in heart murmur classification. A multi-domain subset consisting of 14, both old and new, features was derived using Pudil’s sequential floating forward selection (SFFS) method. This subset was compared with several single domain feature sets. Using neural network classification, the selected multi-domain subset gave the best results; 86% correct classifications compared to 68% for the first runner-up. In conclusion, the derived feature set was superior to the comparative sets, and seems rather robust to noisy data.
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| 4. |
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| 5. |
- Hurtig-Wennlöf, Anita, 1958-, et al.
(författare)
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Heart sounds are altered by open cardiac surgery
- 2009
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Ingår i: Experimental and clinical cardiology. - : Pulsus Group Inc.. - 1205-6626. ; 14:2, s. 18-20
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND OBJECTIVE: Patients have reported that they perceive their own heart sounds differently after open cardiac surgery than before the surgery. The present study was designed to investigate whether changes in heart sounds can be quantitatively measured.METHOD: Heart sounds were recorded from 57 patients undergoing coronary artery bypass graft (CABG) surgery and from a control group of 10 subjects. The so-called Hjorth descriptors and the main frequency peak were compared before and after surgery to determine whether the characteristics of the heart sounds had changed.RESULTS: At a group level, the first heart sound was found to be significantly different after CABG surgery. Generally, the heart sounds shifted toward a lower frequency after surgery in the CABG group. No significant changes were found in the control group.CONCLUSION: Heart sounds are altered after CABG surgery. The changes are objectively quantifiable and may also be subjectively perceived by the patients.
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| 6. |
- Mörner, Stellan, et al.
(författare)
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Parasympathetic dysfunction in hypertrophic cardiomyopathy assessed by heart rate variability: comparison between short-term and 24-h measurements
- 2005
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961 .- 1475-097X. ; 25:2, s. 90-99
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this study, we evaluate cardiac autonomic function in hypertrophic cardiomyopathy (HCM) by assessing heart rate variability (HRV), comparing a short-term laboratory method with an ambulatory (24-h) method, in patients with and without beta-blockade. Reduced HRV is a risk factor for adverse events in some cardiac diseases, but is not a proven risk indicator in HCM. Analysis of HRV has been based on either short- or long-term electrocardiographic recordings and previous studies in HCM have shown conflicting results. There is no consensus on which method to prefer, and we evaluate, for the first time, both short- and long-term analyses in patients with HCM. Long- and short-term HRV analyses were performed in 43 patients with HCM. They were divided in two groups, 22 patients on beta-blockade and 21 non-treated patients. As controls, 121 healthy subjects were used. Young patients without beta-blockade showed a reduction in HRV parameters reflecting parasympathetic function, both in the short- and long-term registrations, which was attenuated by beta-blockade. Parasympathetic autonomic regulation was found to be impaired in young patients with HCM. This may be of clinical relevance as abnormal autonomic function might be a substrate for malignant dysrhythmias. The impairment was attenuated by beta-blockade, which might indicate a clinically useful effect. We also show that short- and long-term methods yield similar results, suggesting that a short-term registration might be sufficient to assess HRV in patients with HCM.
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| 7. |
- Rydberg, Annika, et al.
(författare)
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Serial assessment of variability in heart rate in children with the Fontan circulation.
- 2005
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Ingår i: Cardiology in the Young. - London : Greenwich Medical Media. - 1047-9511 .- 1467-1107. ; 15:5, s. 498-503
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Tidskriftsartikel (refereegranskat)abstract
- Autonomic nervous control of the heart can be studied by analysing variability in heart rate. Although earlier studies have shown reduced variability in patients with the Fontan circulation, we are not aware of any previous study examining longitudinal changes in such children. We have examined 13 patients who had undergone total cavopulmonary connection, and 37 healthy controls matched for age and gender. The examinations included complete echocardiography, and 24-hour ambulatory electrocardiogram for analysis of the parameters for variability in heart rate. After the Fontan procedure, three follow-up examinations were performed at a mean of 4.4 years, 5.6 and 7.2 years. Reduced variability was found in those with the Fontan circulation. A significant difference was found between patients and their controls with respect to high-frequency power at the second, p equal to 0.05, and third, p equal to 0.03, examination. The ratio of low-to-high-frequency components progressively increased in those with the Fontan circulation, a phenomenon that led to a significant difference, p equal to 0.03, at the third examination. Our study shows that, in patients with the Fontan circulation, routine ambulatory electrocardiographic monitoring including analysis of variability in heart rate, detects over time a progressive sympatovagal imbalance.
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| 8. |
- Thunberg, Per, 1968-, et al.
(författare)
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Estimation of ejection fraction and stroke volume using single- and biplane magnetic resonance imaging of the left cardiac ventricle
- 2008
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Ingår i: Acta Radiologica. - London : Taylor & Francis. - 0284-1851 .- 1600-0455. ; 49:9, s. 1016-1023
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Background: In cardiac magnetic resonance imaging (MRI), left ventricular stroke volume (SV) and ejection fractions (EF) are occasionally calculated using single-plane and biplane ellipsoid models. In previous studies, the calculated SV and EF using single- and biplane ellipsoid models have been compared to reference values calculated from short-axis (SA) images. In these studies, however, it has been emphasized that through-plane motion of the basal SA images represents an important source of error, which may result in incorrect reference values.Purpose: To compare the calculated SV and EF using single-plane and biplane ellipsoid models with SV and EF calculated from SA images in which compensation was made for through-plane motion.Material and Methods: A group of 20 patients who underwent MRI examination were included in the study. SV and EF were calculated using the stack of SA images (which had been compensated for through-plane motion) and compared to the SV and EF calculated according to the single- and biplane ellipsoid models.Results: The mean difference between the single-plane model and the reference was -0.3±6.5 for EF and 7.2±17.1 ml for SV. Corresponding comparison between the biplane method and the reference resulted in a mean difference of 0.3±6.1 for EF and 11.8±14.9 ml for SV.Conclusion: The results from this study show that left ventricular EF can be adequately estimated using the single- and biplane ellipsoid models, while SV tends to be overestimated using both geometrical models
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| 9. |
- Thunberg, Per, 1968-, et al.
(författare)
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Separating the left cardiac ventricle from the atrium in short axis MR images using the equation of the atrioventricular plane
- 2008
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Ingår i: Clinical Physiology and Functional Imaging. - Oxford : Wiley-Blackwell Publishing Inc.. - 1475-0961 .- 1475-097X. ; 28:4, s. 222-228
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Tidskriftsartikel (refereegranskat)abstract
- Short axis (SA) images obtained from cardiac magnetic resonance imaging are used to advantage in the calculation of important clinical parameters such as the ejection fraction and stroke volume (SV). A prerequisite for these calculations is the separation of the left ventricle and the left atrium. When only using the information seen in the SA images this separation can be a source of error due to the through-plane motion of the basal part of the left ventricle. In this study a method is proposed where the separation of the left ventricle and the atrium is performed by identifying the intersections of the atrioventricular plane in the SA images. The equation of the atrioventricular plane was determined in both systole and diastole using long axis and four chamber image views. Stroke volumes were measured in 20 patients using SA images where the endocardium had been delineated. The SV obtained using the new method was compared with quantitative flow measurements and the conventional technique for calculation of SV from SA images, respectively. The agreement of SV was, according to Bland-Altman analysis, 2.0 ml (95% CI -12.0 to 15.9 ml) in comparison with the flow measurements and 2.2 ml (95% CI -9.2 to 13.6 ml) compared to the conventional method. Inter- and intra-observer variability, when using the new proposed method, was small. This study shows that the identification of the left atrioventricular plane in SA images can be used in the separation of the left atrium and ventricle.
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